Guardian 4389 Repair Manual page 49

"V-TYPE" PREPACKAGED
TRANSFER SWITCHES
TRANSFER MECHANISM
The 2-pole transfer mechanism consists of a pair of
moveable LOAD contacts, a pair of stationary UTILI-
TY contacts, and a pair of stationary STANDBY con-
tacts. The load contacts can be connected to the utili-
ty contacts by a utility closing coil; or to the standby
contacts by a standby closing coil. In addition, the
load contacts can be actuated to either the UTILITY
or STANDBY side by means of a manual transfer
handle. See Figures 2 and 3.
STANDBY
LOAD
Figure 2. Load Connected to Utility Power Source
STANDBY
LOAD
Figure 3. Load Connected to Standby Power Source
UTILITY CLOSING COIL C1:
See Figure 4. This coil is energized by rectified utility
source power, to actuate the load contacts to the
UTILITY power source side. When energized, the coil
will move the main contacts to an "overcenter" posi-
tion. A limit switch will then be actuated to open the
circuit and spring force will complete the retransfer to
STANDBY. A bridge rectifier, which changes the utili-
ty source alternating current (AC) to direct current
(DC), is sealed in the coil wrappings. If coil or bridge
rectifier replacement becomes necessary, the entire
coil and bridge assembly should be replaced.
STANDBY CLOSING COIL C2:
Coil C2 is energized by rectified standby source
power, to actuate the load contacts to their "Standby"
source side. Energizing the coil moves the load con-
PART 3
UTILITY
UTILITY
DESCRIPTION & COMPONENTS
tacts to an overcenter position; limit switch action
then opens the circuit and spring force will complete
the transfer action to "Standby". This coil's bridge rec-
tifier is also sealed in the coil wrappings. Replace the
coil and bridge rectifier as a unit.
LIMIT SWITCHES XA1 AND XB1:
Switches are mechanically actuated by load contacts
movement. When the load contacts are connected to
the utility contacts, limit switch XA1 opens the utility
circuit to utility closing coil C1 and limit switch XB1
closes the standby circuit to standby closing coil C2.
The limit switches "arm" the system for retransfer
back to UTILITY when the load contacts are connect-
ed to the STANDBY side. Conversely, when the load
contacts are connected to the UTILITY side, the
switches "arm" the system for transfer to STANDBY.
An open condition in limit switch XA1 will prevent
retransfer to "Utility". An open switch XB1 will prevent
transfer to STANDBY.
N2A A
BRIDGE
RECTIFIER
UTILITY
CLOSING
COIL (C1)
LIMIT
SWITCH
(XA1)
MANUAL
TRANSFER
LEVER
LIMIT
SWITCH
(XB1)
STANDBY
CLOSING
COIL (C2)
BRIDGE
E2
RECTIFIER
Figure 4. The "V-Type" Transfer Mechanism
TRANSFER RELAY
Transfer relay operation is controlled by a circuit
board. That circuit board is a part of a control panel
assembly, mounted on the standby generator set.
Figure 5 shows the transfer relay pictorially and
schematically. Relay operation may be briefly
described as follows:
1. Generator battery voltage (12 volts DC) is available to
the transfer relay coil from the generator circuit board,
via Wire 194 and Relay Terminal A.
a. The 12 volts DC circuit is completed through the
transfer relay coil and back to the generator cir-
cuit board, via Wire 23.
b.Circuit board action normally holds the Wire
23 circuit open to ground and the relay is de-
energized.
SECTION 3.1
N1
N2
E1
E2
T2
B
T1
Page 47
A
126
205
B